On a regular basis, something like every 10 - 20 minutes, CGPro
does... something, for 5 - 15 seconds. During that time it delays
interactions with MUAs. From the user's point of view it all they see is
the busy spinner. It is annoying.
There is nothing in the server's logs to indicate the momentary
catatonia. There is nothing in the system logs.
This is something that became noticeable several versions ago,
somewhere around 6.1.12. It has become more of an issue with each upgrade.
The only clue I have is what "nmon" displays in its CPU usage: a spike
in CPU usage, up to 70%, consisting of wait states. These always occur
when CGPro is briefly unavailable.
Access to the server is on our local network, not from the Internet.
We have a couple of helpers running, one each for DKIM and DMARC.

Can anyone suggest what may be happening? Or how to discover what is
happening.

First of all, I'd advice you to monitor basic perfomance indicators. For example, you can use atop to see the history of memory/network/disk utilization. High "wa" field in the top's output during the "catatonia" may suggest problems with storage. You can use smartctl tool to examine the health of your disks.

You can send more specific info about your installation to support@communigate.com. Details like your server's hardware configuration, number of active account and list of providing services. Also full non filtered log file may help us to indicate the problem.

--
Best regards,
Anton Babinov
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